The exact cause of Chronic Myelogenous Leukemia (CML) is unknown. However, research suggests that it is caused by a genetic mutation in the bone marrow cells. This mutation is known as the Philadelphia chromosome, which is caused by a translocation of genetic material between chromosomes 9 and 22. This mutation leads to the production of an abnormal protein, known as BCR-ABL, which causes the uncontrolled growth of white blood cells. Other possible causes of CML include exposure to radiation, certain chemicals, and certain viruses.